Hepatitis E virus (HEV), the causative agent of hepatitis E, is an important public health problem in developing countries. HEV is also considered to be endemic in the United States (U.S). HEV strains recovered from patients in the U.S. are remarkably similar genetically to the swine hepatitis E virus (swine HEV) isolated from pigs in the U.S. Due to the lack of a practical animal model and an in vitro cell culture system, the replication and pathogenesis of HEV is poorly understood and a vaccine for HEV is still not available. This proposal is based on a recent discovery by the candidate of the swine HEV, the first and only animal strain of HEV identified to date, and its ability to infect across species. Swine HEV infects non-human primates and, reciprocally, a U.S. human strain of HEV infects pigs. The long-term objectives of the proposed research are to understand the mechanisms of HEV replication and pathogenesis by using HEV infection in pigs as a model system. The central hypothesis in this proposal is that swine HEV infection in swine mimics HEV infection in humans and thus, is a useful animal model for HEV. The proposed experiments are aimed to systematically characterize the course of HEV pathogenesis, to evaluate swine HEV infection in pregnant pigs as an animal model for fulminant hepatitis E that often occurs in pregnant women, and to identify the primary and extrahepatic sites of virus replication in experimentally- infected pigs. This will be accomplished by utilizing standard techniques including in situ hybridization, PCR, immunohistochemistry and serological and pathological methods. Secondly, the candidate hypothesizes that the hypervariable region (HVR) of HEV is important for virulence. The candidate aims to construct a full-length infectious cDNA clone of swine HEV and a swine-human HEV chimera in which the HVR of swine HEV will be replaced with that of a human strain of HEV. The pathogenicity of the clones will be studied by direct intrahepatic inoculation of the cDNA transcripts into the animals. The proposed studies will significantly advance our understanding of the mechanisms of HEV replication and pathogenesis, and the information gained from this study will be critical for devising strategies for prevention and control of this important disease. This award will enable the candidate to gain valuable experiences in the field of comparative viral pathogenesis, and will be instrumental for the candidate to build a successful and independent research career in biomedical sciences.